1. Field of the Invention
The present invention relates to an ion exchange membrane fuel cell, and more specifically, to an ion exchange membrane fuel cell module which is incorporated into a fuel cell power system.
2. Description of the Prior Art
The operation of fuel cells are well known. A fuel cell generates electricity from a fuel source, such as hydrogen gas, and an oxidant such as oxygen or air. The chemical reaction does not result in a burning of the fuel to produce heat energy, therefore, the thermodynamic limits on the efficiency of such a reaction are much greater than conventional power generation processes. In a proton exchange membrane fuel cell, the fuel gas (hydrogen) is ionized on one electrode and the hydrogen ions diffuse across the membrane to recombine with oxygen ions on the cathode. The byproduct of the reaction is water and the production of an electrical current.
In our application Ser. No. 08/979,853, now U.S. Pat. No. 6,030,718, the inventors disclosed a new and novel proton exchange membrane fuel cell power system which includes a plurality of discrete fuel cell modules which are self-humidifying and which offer a degree of reliability, ease of maintenance and other advantages not known heretofore with respect to fuel cell designs which have been primarily directed to stack-type arrangements. The teachings of this earlier patent are incorporated by reference herein.
While the modular fuel cell disclosed in the earlier patent referenced above operates with a great deal of success, the inventors have endeavored to improve upon this inventive concept by focusing further investigation on increasing the performance, versatility, and the range of the operational parameters of fuel cells of this general design.
Accordingly, an ion exchange membrane fuel cell which achieves the benefits to be derived from the aforementioned technology, but which avoids the detriments individually associated with stack type fuel cell designs is the subject matter of the present invention.
One aspect of the present invention is to provide an ion exchange membrane fuel cell having multiple modules each enclosing a membrane electrode diffusion assembly, and wherein at least one of the modules can be easily removed from the ion exchange membrane fuel cell, by hand, while the remaining modules continue to operate.
Another aspect of the present invention is to provide an ion exchange membrane fuel cell having a module enclosing a membrane electrode diffusion assembly which has an active area defined by a surface area, and which produces an average current density of at least about 350 mA per square centimeter of surface area when supplied with a dilute fuel at a nominal voltage of about 0.5 volts.
Another aspect of the present invention is to provide an ion exchange membrane fuel cell power system having a plurality of discrete ion exchange membrane fuel cell modules which can be manipulated by hand, and which further produce a given amount of heat energy, and wherein each of the discrete ion exchange membrane fuel cell modules have an anode heat sink which removes a preponderance of the heat energy generated by the respective ion exchange membrane fuel cell modules.
Yet further, another aspect of the present invention is to provide an ion exchange membrane fuel cell power system which has an ion exchange membrane fuel cell module which produces heat energy and which has a bifurcated air flow which regulates the operational temperature of the ion exchange membrane fuel cell module by removing the heat energy therefrom.
Yet another aspect of the present invention relates to an ion exchange membrane fuel cell module having a pair of membrane electrode diffusion assemblies disposed in spaced relation, one to the other, and wherein each membrane electrode diffusion assembly has an anode side, and an opposite cathode side, and wherein the cathode side of each of the membrane electrode diffusion assemblies are proximally related, and the anode sides are distally related, and wherein each cathode side defines, in part, a bifurcated cathode air passageway.
Another aspect of the present invention relates to an ion exchange membrane fuel cell module having a pair of membrane electrode diffusion assemblies each having opposite anode and cathode sides, and wherein anode and cathode current collectors are electrically coupled with the opposite anode and cathode sides; a support member disposed between the pair of membrane electrode diffusion assemblies, and wherein the cathode side of each membrane electrode diffusion assembly faces in the direction of the support member; a cathode air passageway defined between the support member and the cathode side of each of the membrane electrode diffusion assemblies; a fuel distribution assembly coupled in fluid flowing relation relative to the anode side of each membrane diffusion assembly; and an anode heat sink oriented in heat receiving relation relative to the anode side of each membrane electrode diffusion assembly to facilitate the removal of a preponderance of the heat energy generated by each membrane electrode diffusion assembly.
These and other aspects of the present invention will be discussed in further detail hereinafter.